Cold starting motor fuel



y 1949- w. J. SWEENEY 2,469,751

cow STARTING MOTOR FUEL Filed Sept. 1, 1945 2 Sh eets -Shee t 1 7 12 inbyc Fuel. .s-rozeAca TANK 4 L L Z ,6 a 1 (ENG/NE OPERATING r051.

$7072.46: TAYK 75 l3 7 T An:

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wJJ, SWEENEY COLD STARTING MOTOR FUEL 2 Sheets-Sheet 2 Filed Sept. 1, 1943 3 O E w M r 13 0 ml wmnm 2 22 Q 9 000 U frrr Q a r. if 2 m H a u r u w r N L L U a U F n r n H n 0 0 0 o 0 o 0 o 0 m H m m 8 6 a. z

2. a F Fla-z Patented Ma 10, 1949 I UNITED 'STATES PATENT OFFICE COLD STARTING MOTOR FUEL William J. Sweeney, Summit, N. 1., assign'or to Standard Oil Development Company. a corporation of Delaware Application September 1, 1943, semi No. 500,154 2 Claims. (01. 44-52) The present invention relates to an improved method for starting gasoline engines at low temperatures and to a'prlming fuel especially adapted for the processfjl'he invention will be fully understood from the following description and the drawings.

Fig. l is a diagrammatic plan of the equipment required for starting the engine at low temperature by the present method, and

Fig. z'shows distillation curves of several fuels made up according to the invention and indicates their characteristics.

Everyone who has operated a motor car in cold weather knows the increased difficulties of starting the engine at progressively lower atmospheric temperature. With airplanes these difflculties are perhaps even greater since it is frequently necessary to start motors at temperatures far below those at which automobiles are apt to be operated. For example, it is a common occurrence in some localities to encounter atmospheric temperatures of 20, 30 or even -65, and it is desirable to have some general method, fuel and procedure which is capable of starting engines at these low temperatures, and particularly a method and particular fuel which can be successfully used over this entire range of temperature without variation.

The starting of cold motors is an old problem and long ago it was proposed that special priming fuels be employed, that is to say, that the engine be started on a special fuel, generally lighter and lower boiling than the ordinary operating fuel. Such attempts have not, however, been successful, particularly at the very low temperatures far below zero. One reason for this lack of success lay in the nature of the particular fuels that were used and, secondly, in the method in which they were employed.

Prior priming fuels have in almost every case consisted of extremely narrow range cuts of light petroleum hydrocarbons, in many cases pure hydrocarbons, principally propane, butane. and the like. On the contrary it has now been found that the fuel best suited for this purpose is a relatively wide cut mixture of several volatile hydrocarbons of different boiling points. The prior methods have depended either on the direct discontinuousinjection of a choking stream of fuel or ontheapplicationof the priming fuel,

just asthe operating fuel was used, that is to say, it was evaporated into the air stream and was carried into the. engine along with and roughly proportional to the amount of air fed. In contrast. the-present method consists of continuously,

2 forcing a stream of liquid fuel into the intake manifold quite independently of the air stream and the fuel is so composed that it is vaporized in such an amount that the vaporized quantity always forms an explosive mixture with air. Any

- excess remains as liquid and is removed in this form without combustion. Thus the method depends on the continuous feeding of an excess of liquid fuel during theentire starting period so that the amount vaporized always forms a combustible mixture under the entire range of starting conditions.

Referring to the drawing, Fig. 1 is a diagrammatic plan of the equipment required for the present process. Numeral l denotes a storage tank for the priming fuel which will be described for the present as a wide cut mixture of normally gaseous and low boiling hydrocarbons. The supply tank need not be described in detail and it will suiiice to say that it is of any type suitable for the storage of very volatile products which may have 9. Reid vapor pressure of 40 to 75 pounds per square inch. The fuel is drawn in liquid condition through the line 2 by the fuel pump 3 and aby-pass line is provided around the pump and fitted with a valve 4, so that the pump may be operated at a constant speed, and by adjusting the valves 2' in the feed line 2 and valve 4 in the by-pass line, it is possible to deliver an adjusted amount of fuel to the engine while the pump is operating at a constant speed. The fuel line 2 discharges the liquid fuel into the engine manifold 5 at any convenient point, preferably at the entrance of the supercharger which is indicated at 6. A suitable cranking device isv shown at I and the ignition switches at 9. The operating fuel tank is number It and the ordinary fuel is withdrawn by the pipe II which contains the valve l2 and the fuel pump IS. The fuel pump has a by-pass line l3 similar to that supplied with the priming fuel pump so that this pump may be operated at a constant speed without delivering any fuel to the engine when the valve I2 is closed and I 3' is opened. This fuel is injected into. the engine at ll, while the air enters in the usual way at l5, and is measured by the carburetor it which discharges in the usual manner into the intake manifold 5.

In the operation of the present process, the engine will naturally be at atmospheric temperature and the priming fuel pump 3 is started with valves 2 and 4 being adjusted so that the desired volume of fuel is forced at a pump pressure of 2 to 50 pounds through the line 2 and into the engine manifold. The amount of fuel supplied should be calculated so as to be sumcient to operate the engine under idling conditions, with a slight excess, say to It will be understood that the operating fuel pump [3 is also set in motion, but the valve [2 is closed so that none of-the operating fuel is delivered to the engine. The engine is now spun by the use of the cranking device I and when the engine speed reaches a proper value, the switch 9 is closed so that the priming fuel is ignited and the engine starts. The speed at which the engine muzt be spun cannot be specified with exactness since it is primarily a function of the particular engine, its design and construction, and the lubricants used, but in general it will be of the order of 50 R. P. M.

The priming fuel is allowed to flow for several seconds before the switch 9 is closed, and even after ignition, it is desirable to operate the engine on the priming fuel for 30 to 120 seconds in order to warm up the engine. At the end of this time, valve 2' is closed and the valve I2 is opened simultaneously so that the operating fuel is substituted for the priming fuel.

The various operations indicated before may be effected by hand or mechanically and with the proper fuel it has been found that various types of engines can be consistently started at temperatures over the range of --65 to F. easily and quickly. Slight variations in the operation may be desirable, depending on the particular engines, just as indicated about, where desired rotational speed of the engine may be varied and in the same manner the amount of fuel required is also variable. I

From what has been said, it will be appreciated that the composition of the priming fuel is a most important feature in the present invention and the success of the method depends on the use of a fuel consisting of a liquid mixture of several normally gaseous and liquid hydrohaving a wide boiling range, that is to say, a boiling range of at least 75 Fahrenheit degrees between the 10% and 90% distillation points. It is preferable to provide even a greater spread than this, for example 100 or even 150 Fahrenheit degrees.

The fuel must contain a sufficient amount of very volatile constituents, which will be vaporized at the lowest starting temperature likely to be encountered. In addition to these fractions, there must also be intermediate constituents boiling between the low boiling initial fractions and the volatile fractions of the operating fuel. Such fractions serve to fill the gap between the starting fractions and the operating fuel. It will be understood that the proportions of these various light, intermediate fractions are of extremely great importance. If the quantity of the lighter fractions is too great, there would be difiiculties in starting at temperatures from -20 to +20 F., and also there is a considerable tendency to vapor locking at these temperatures. Storage and handling difficulties are also increased. If, on the other hand, an insufficient quantity of these materials is provided, the fuel will fail to start at the very low temperatures. It is particularly important that there should be, as stated before, a wide boiling range in the fuel.

As to the actual composition of the fuel, it is made up principally of the hydrocarbons from propane to octane and it is preferred to use a substantial quantity of the iso compounds becarbons, ranging from 3 to 8 carbon atoms, and v at all times.

cause of their superior anti-detonation quality. Ethane or ethylene are not absolutely required, although it is desirable to provide from 2 to 3% by volume and not more than about 5%. The amount of propane and propylene, that is to say, C3 hydrocarbons, will vary between about 10 and 25%. The butanes, C4 fractions, vary from about 15 to 45% and the pentanes, C5 fractions, from 30 to 40%. In addition to the Ca through C5 fractions. it is also preferable to add a certain amount of the heavier components which may be selected from the hexanes, heptanes and octanes. This is preferably in from 10 to 25% of the final fuel mixture and instead of these pure compounds, if desired, ordinary gasoline can be added or, if preferred, aviation gasoline which supplies these heavier components.

The above percentages may be looked upon as limits and it will be understood that the fuel is thus balanced so as to give a smooth boiling curve which has the following characteristics:

It will be understood that olefins may be used instead of parafiins or mixtures of olefins and paraffins may be used and various fuel ingredients may be added also, such as top lubricants, antidetonation agents, inhibitors and the like, just as in any other fuel.

In further explanation of the present method, it may be said that an engine must be operated on a mixture of vaporized fuel and air in which the proportion of fuel to air, that is to say, the air-fuel ratio, must be at all times within the explosive limits. These limits are definite characteristics of the fuel itself and are such that a mixture may be too lean or too rich for ignition. In the usual method of operating gasoline engines, the fuel is vaporized in the inlet air and most prior attempts to solve the low temperature starting problem have supplied the fuel with the air in the usual manner, that is to say, the flow of air controlling the flow of fuel either by evaporation or mechanically. If a pure hydrocarbon, such as propane or butane is used, the explosive limits of the mixture are quite narrow, of the order of 20 to 25 Fahrenheit degrees, and it is very difficult, practically impossible, in the ordinary method of operation to keep the mixture constantly within this narrow range, where explosion is possible. When prior priming fuel vaporizes, there is a drop in temperature and this is frequently enough to bring the mixture out of th explosive range. Furthermore, when an engine starts, its speed rapidly increases and.

its temperature also rises, which makes it almost impossible to adjust the volume of fuel to air so as to hold the fuel-air mixture within the narrow explosive range within the very short time available to the operator. No simple mechanical device has been found to accomplish this desired result. In other words, the changes in temperature and other conditions are so rapid during the starting period that it is impossible for an operator to maintain the mixture con stantly within th explosive range and the air volume is not a suitable control means by which the requisite amount of fuel can be provided This is thought to be the reason for the sputtering and stalling which is so gener- 8 ally met in attempting to start an engine at low temperatures. In the present invention, these faults are corrected first by feeding the fuel, ina dependent of the air, constantly and at a rate sufficient for the operation of the engineunder the starting conditions or slightly in excess thereof. The fuel is fed as a liquid and not along with the air in vaporized condition. Thus a considerable volume of fuel is constantly'being supplied and is always available to be vaporized as needed. Some of the priming fuel, especially at low temperatures before the engine is warmed up, will .not be vaporized at all and will be discharged from the engine as a' liquid unburned but the important point is that as the engine speed is increased and as the temperature rises, sufiicient fuel is always present forvaporization as required. The second important point to be understood is that the fuel itself being a wide out rather than a very narrow cut, is characterized by a wide range of explosive limits rather than narrow. explosive limits. For example, instead of the 20 to 25. characteristic of a pure hydrocarbon of the lower range, the present mixtures have ranges in excess of 100 Fahrenheit degrees, and preferably of 200, 250 or even 300 Fahrenheit'degrees. This permits a wider ran e of possible operation and the sputtering and stalling is then practically eliminated, since sumcient time is given for adjustment within the explosive range. From the above is will be apparent that the present method requires the particular fuel, or in other words, the composition of the priming fuel is a feature of the method itself.

As examples of the types of priming fuels,the following may be considered typical:

Example 1 63353 Percent By Weight i it? its;

S 11 e v a e 122 lz-s SODGD 8116.- N-pentane 16.0 10. a} 6% Pentium Nechexane 18. 4 20.1

This fuel had a Reid vapor pressure of 56.5 pounds and was quite satisfactory over a wide range from 60 F. to +200 F. The boiling range has been plotted in Fig. 2, as fuel #1.

pounds. It was also quite satisfactory at low temperaturesbut had a tendency to vapor lock at 0 F. to 20 F. Its distillation curve is also plotted in Fig. 2. These distlllations are carried out with a fluid immersed in a mixture of alcohol and dry ice condensed in the same manner, the temperature being recorded in the same manner as is familiar in the Engler distillation firocedure. This fuel was distilled twice on successive days and both curves are plotted in Fig. 2 as fuel #2 and #20. in order to indicate the degree of reproducibility.

V Example 3 The fuel of this example was made by adding to an aviation gasoline certain low boiling hydrocarbons.

Percent By Percent By Volume Weight Propane 20 11.0 Tenhnbnm N-hutane 28. 2 27. 0 Isopentane 34. 5 36. 0 N-pentam Aviation Gasoline 17. 3 20 The aviation gasoline had the following characteristics:

Gravity A. P. I. "degrees-.. 68.8 Reid v. P. 0.1 ASTM distillation:

% at F 140 50% at F- 158 90% at F 1'78 Final F 199 This complete fuel had a Reid vapor pressure I of 65% pounds. In tests with this fuel, a Wrightv engine, type G-2600, was started successfully and consistently at the following temperatures: F., 40 F., F., F. and F. The fuel was fed independent of the air at a pressure of about 10 pounds per square inch. The spark timing was about 20 before top center and throttle setting was 9 from the horizontal closed position. Cranking speed was 50 R. P. M. and the fuel was fed into the air line just at the entrance of the supercharger. The feeding of the priming fuel was continued for from 30 to 120 seconds after the engine took hold, before the ordinary operating fuel was substituted for the priming fuel. This was accomplished easily and smoothly. The operation was marked by the absence of false starts, sputtering and stalling.

From the above description, it will be understood that many minor changes in thefuel are possible within the ranges given. Certain hydrocarbons may be eliminated altogether without pronounced ill effect. For example, hexane is absent in the fuel of Example 2, but it is believed best to include in all fuels propane, butane and pentane and some of the higher hydrocarbons which may be selected from the group of hexane, heptane and octane or, better, to use a portion of gasoline, say an aviation gasoline which will contain these several hydrocarbons. As stated before, ethane is not necessary but up to 5% may be included and it is of assistance in.

starting when the extremely low temperatures are encountered.

I claim:

1. A priming fuel for starting gasoline engines at low temperatures comprising a liquid mixture of normally gaseous and low boiling paraflinic hydrocarbons, 10% to 25% having 3 carbon atoms, 15% to 45% having 4 carbon atoms, 30% to 40% having 5 carbon atoms, along with 10% to 25% of heavier gasoline constituents, said fuel exhibiting the following distillation curve:

10% evaporated between and +300 F.

50%, evaporated between 50 and 100 F. evaporated between and F. 2. A priming fuel for starting gasoline engines at low temperatures comprising a. liquid mixture of normally gaseous and low boiling parafllnic and olefinic hydrocarbons, to having 3 carbon atoms, 15% to 45% having 4 carbon atoms, to having 5 carbon atoms, along with 10% to 25% of heavier gasoline constituents, said fuel exhibiting the following distillation curve:

10% evaporated between -30 and +30 F.

% evaporated between 50 and 100 F.

% evaporated between and F.

WILLIAM J. SWEENEY.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER REFERENCES Nash and Howes, "Principles of Motor Fuel Preparation and Application" (1935),, vol. 1, page 129. 

